Chemical Inhibitors of ER stress. Disturbances in the normal functions of the endoplasmic reticulum (ER) lead to an evolutionarily conserved cell stress response, the unfolded protein response (UPR), which is aimed initially at compensating for damage, but eventually, can trigger cell death if ER dysfunction is severe or prolonged. The mechanisms by which ER stress leads to cell death remain enigmatic, with multiple potential participants described but little clarity about which specific death effectors dominate in particular cellular contexts. Important roles for ER-initiated cell death pathways have been recognized for several diseases, including hypoxia, ischemia-reperfusion injury, neurodegeneration, heart disease, and diabetes. The goal of this application is to identify chemical compounds that block cell death induced by ER stress. A cell-based assay has been devised which is simple and effective for identifying such compounds. Several supporting secondary assays have also been devised that inform compound characterization. Proof of concept data are presented that validate this chemical biology approach for generating compounds that will become useful research tools for interrogating mechanisms of ER stress-induced cell death and dysfunction. 1 Essentially all cells possess the ability to produce proteins that are either displayed on the cell surface for purposes of sensing changes in the environment or that are secreted from the cell. The organelle within the cell responsible for this function is called the "endoplasmic reticulum" (ER). Defects in protein folding in the ER trigger an evolutionarily conserved cellular response that can activate programs for cell death and thus destroy cells. This protein folding problem is termed "ER stress" and it has been associated with a wide range of diseases, including ischemia-reperfusion injury (particularly stroke), neurodegeneration, and diabetes. In this proposal, we seek to identify chemical compounds that inhibit cell death induced by ER stress. These chemicals will be useful research tools for dissecting mechanisms of ER stress in the laboratory, and may also serve as the starting point for generation of novel medicines that preserve brain cells during stroke or neurodegeneration, or that overcome the effects of ER stress responsible for worsening insulin-resistance, thus improving diabetes care. [unreadable] [unreadable] [unreadable]